London has been battered by 50mph winds that have felled trees and caused travel chaos. Powerful gusts swept across the capital as the Met Office issued a yellow "be aware" weather alert for most of the country.

Boris Johnson has threatened large housing developers sitting on land until its value goes up with tough compulsory purchase orders unless they start building.

The Mayor criticised “pernicious land-banking” which he said was against London’s economic interests and was contributing to the housing crisis.

There are thought to be up to 177,000 new housing units in the capital with planning permission in place but where the development has stalled, although not all as a result of land-banking. Mr Johnson told the London Assembly: “It’s pernicious and I would be prepared to use CPO powers.

“To constrict supply to push up prices by land-banking is plainly against the economic interests of this city.

“I’m all in favour of using the powers where there are clear cases ofl and-banking, where people could go ahead with developments that would be massively to the benefit of this city.”

The Mayor is able to begin the CPO process to try to obtain the land without the consent of the owner.

However, the decision whether to force the sale would be taken by independent planning officials appointed by the Government. They would also set the value.

CPOs are a legally complicated and expensive process and usually used only in rare circumstances where a proposed development is considered to be for the public good — for example when building a motorway or redeveloping a town centre, and where the landowner does not want to sell.

Mr Johnson warned he would still have to respect property rights “to a certain degree” suggesting he does not plan to embark on a large-scale programme of CPOs.

“We don’t live in a Stalinist system. Private property is what it is, you can’t just take it off people willy-nilly, this isn’t Zimbabwe.

“The reason schemes don’t go ahead is not just because of the greed of developers,” he said.

The Mayor has come under pressure from opponents to make sure that big developers are not allowed to welch on their affordable housing commitments.

But he suggested numbers could be cut in order to get them building.

“I’d rather see these schemes go ahead with some affordable housing than not go ahead at all,” he said.

Former Labour deputy mayor Nicky Gavron welcomed the move to use CPOs to unblock developments but added: “We’re looking at bare profits going up and affordable housing going down.

“We need to get these schemes moving without forfeiting the affordable housing.”